The invention concerns a method for measuring the total length of winding material being wound onto a winding beam.
These types of methods are mainly known and in use with beaming and sectional warping machines of various types. The material to be wound mostly concerns yarns, guided in the form of a strip.
Here, it is important that the length of the material being wound is exactly measured. In practice, for determination of the length, the material being wound is guided over a measuring roll for determination of the total length. Slippage occurs between the material being wound and the measuring roll during braking and, acceleration procedures, the extent of which is not easy to establish. This results in length measuring errors: during running up to speed, a certain time is required until the measuring roll is accelerated at a synchronous speed with the material to be wound, and during braking the measuring roll will rotate further due to its rotational inertia. In the following description, the operating phases when slippage occurs on the measuring roll will be termed slippage operation, the phases without slippage will be termed continuous operation.
Dispensing totally with the measuring roll has already been recommended. Thereafter, the total length should be ascertained from the rotational speed of the wound package and the circumference of the wound package. This has, however, proved difficult since the smallest error when asertaining the thickness of the wound package will lead to a considerable discrepancy between the calculated length value and the actual length value.
Switching between two measuring methods during operation has therefore been recommended in DE-3215322. In continuous operation, the length of the wound package is measured by means of a measuring roll arrangement. In addition, a second measuring method is provided, where the wound length is calculated from the rotational speed of the wound package and the circumference of the wound package. The arrangement further incorporates a device which can detect the occurrence of slippage on the measuring roll. Such devices are, for example, described in DE-3215322, from Schlafhorst. This device is used for switching between the two measuring methods in such a way that during continuous winding operation, the measurement is executed by means of the measuring roll, and with the occurrence of slippage, immediate switching to the alternative measuring method is initiated. With that method, the length is deduced from the number of rotations or partial rotations multiplied by the respective circumference of the wound package. This measuring method is maintained until the continous winding operation is once again attained; the method then reverts to measurement by means of the measuring roll.
A difficulty with the known arrangement is to determine the circumference of the wound package during slippage operation as exactly as possible: the accuracy of the desired length measurement is dependent on this. Here, measurement of the wound package circumference during continuous operation has been recommended, in order then to have this available when slippage occurs. For that, the length of the winding material wound during one rotation of the wound package is measured on the measuring roll. This measurement is executed at each rotation of the wound package and the measurement value ascertained is stored in an intermediate memory. When slippage occurs, switch over to measurement by means of rotational speed and the circumferential length of the wound package will be initiated, the last circumferential length to have been measured being available in the mentioned intermediate memory. Now, after each rotation of the wound package, the total length is increased by the stored circumferential length. This is maintained until continuous winding operation reinstates itself. If slippage on the measuring roll prevails during several rotations, the additional problem will arise that the circumference of the wound package will not remain constant, but will increase with each rotation of the wound package. In order to correct this error, increasing the last ascertained circumference of the wound package by a constant correction value with each further rotation has thus been recommended. This correction value is to be ascertained by means of a table, on the basis of parameters such as, for example, yarn material and yarn spacing. The input of such correction values is, in practice, extremely time consuming. Apart from that, the correction values are inaccurate and lead to measurement errors mainly during more lengthy slippage operation.